Alloy



UNITED STATES PATENT OFFICE.

man rncz, or cnnvnmm: nnrenrs, 01:10. i

- Patented Aug. 16, 1921.

- To all whom it may concern used commercially.

In the making of crank cases and pistons for internal combustion motors, of disk wheels, floor plates and running boards for vehicles, casings for suction cleaners, culinary utensils, machine parts and patterns and a great many other purposes, it is desirable to employ a castin metal of considerable rigidity and very llght-weight, one of the requirements being that the metal shall be susceptible of easy machining. One of the best known and most used of these alloys has been thatknown as No. 12 metal which consists approximately of aluminum 92, copper 8, sometimes with a very'small addition of iron. This metal ordinarily possesses tensile strength of from 17 ,000 to 18,000 pounds per square inch with an elongation of from one to one and one-half per cent., and with present prices of ingredients (aluminum 33 and copper 20 per pound) costs about $640.00 per ton.

The objects of my invention are the provision of a metal which shall cast fully .as well as any aluminum alloy heretofore known; .whichshall have a lower coeflicient of heat expansion than other aluminum al.-

loys and hence shrink less on cooling; which shall have a higher tensile strength and a higher elongation than any known aluminum" alloy of equal density; which shall be as easily machined, and shall be lower in price; which shall yield perfect castings throughout a wide range of pouring temperatures; while further objects and advantages of my invention will become apparent as the description proceeds.

My improved composition is characterized by containing upward of 80% of aluminum combined with at least about 5%- of silicon, withor without small additional quantities of other metals, such for example as a small of the whole.

Application filed February 18, 1920. Serial No. 358,555.

amount of iron, but those other metals preferably constituting not over about 2% The presence or absence of the last namedmetals is not considered as bearing .upon my invention, which derives its principal characteristics from the combination of aluminum with the comparatlvely large amount of silicon mentioned; and the preferred species is that containing aluminum and silicon in the proportion of approximately seven to one regardless of the presen'ceor absenceof small quantities of additional elements, although any composit1o n containing between 8% and 15% of SlllCOIl lies within a very valuable range. It has heretofore been supposed that the largest amount of silicon which could be incorporated with aluminum was about one half of one per cent., and I am able to secure the assimilation of this comparatively large quantity only by the employment of a gram-refining process certain of whichI will now describe.

I preferably produce my improved alloy by melting together commercial aluminum and commercial metallic silicon, ordinarily of about 90% pure silicon together-with about 10% chief of which are silica, carborundum, iron silicid, calcium silicid, aluminum, and iron. According to my preferred procedure I first melt together 1 part of this material with 4 parts of aluminum in a suitable crucible and after the batch has become thoroughly melted, decant the same either into another crucible or into suitable ingot molds, this being for the purpose of removing the nonmetallic impurities which become incrusted upon the interior of the crucible. I then add further aluminum to this mixture in any proportion from about 25% to 50%; if less than about' 25% of additional aluminum be employed, the resulting alloy becomes increasingly brittle and above about 50% of additional aluminum, the resulting alloy be comes increasingly soft, although I do not restrictwmyself exactly to these limits inasmuch as there are some uses for which the same can be exceeded without danger. I preferably employ about 33% of added aluminum to 66% of the first mixture, whereby there is produced the preferred composition first mentioned, namely aluminum 7, silicon 1. His equally within my invention and produces the same ultimate alloy to melt the consisting ingredients directly together in the final proportion desired, but the same is less convenient. practically because of the larger quantity of material necessary to handle during the refining operation.

The resulting alloy if cast directly has a very coarse, dark, crystalline fracture and its physical pfoperties are quite low, sile strength running from about 15,000 to 18,000 pounds per square inch with an elongation of from one-half er cent. to one and one-fourth per cent. owever, before casting this metal into the finished form, I treat it at a temperature above its melting point, with an alkaline fiuoridor a combination of fluorids, one at least of which is that of an alkali: for example, sodium fluorid, potassium fluorid or lithium fluorid either alone or mixed with calcium fluorid, barium fluorid, strontium fluorid or magnesium fluorid. I preferabl employ sodium fluorid as a base and use at east about one per cent. of the same by stirring the pulverized compound into. the molten metal with a carbonrod, whereupon a yellow flame appears suggestive of the combustion of metallic sodium, accompanied by a dense, acrid, white smoke. This stirrin is continued rather briskly until the evo ution of flame and smoke ceases. If now the metal be cast, it will be found that the fracture instead of being coarse, dark and glassy, is fined dense. The physical able change, the tensile strength rising to a point between 23,000and 27,800 pounds per square inch and the elongation to a point between 3%% to 61%. 'Accordingly the composition is stronger than any commercial casting alloy of equal density, being fully ten per. cent. lighter than the Number 12 -metal heretofore mentioned and at the present prices of ingredients (silicon 13 per pound) costs only $600.00 per ton as (gamst $640.00 for Number 12 metal. ompared 'by volume with Number 12 metal my alloy is the cheaper in the proportion of 6 to 7 and upon the. basis of the tensile strength my improved cbmpositionjs superior to Number 12 metal inthe proportion of 6 to 9. The castings run freely, expand s'ufliciently on solidification to copy the mold ,with great exactness, shrink on coolmg less than any other known aluminum alloy, are 'free from blow-holes or pin-holes,

. can be readily machined, and take and re- --lent for die castings,

tain a high polish. My alloy is also exceland after the alkali fluorid treatment herein described it can be forged and drawn into wire and possesses considerable ductility when cold.

' Furthermore these successful castings can be secured without any special care as. to

temperatures, which is a very important feature in comqnercial foundry practice.

the tenaluminum;

I do not confine myself to any one source of silicon; I do not exclude the use of additional metallic ingredients so long asthe amounts of silicon and aluminum are re-' tained within the relative proportions herein mentioned; I do not restrict myself to the addition of an alkaline fluorid only in the precombined state since I have had excellent results by using a mixture of sodium chlorid and calcium fluorid and I conceive that other fluorid compounds can be em ployed; and I do not limit myself to any theory of operation but only set forth herein the results of my actual observations and discoveries, restrictin myself to details only as specifically recite in the claims hereto annexed. The present application is limited to the alloying and treatment of alloys containin aluminum and silicon, the more general idea of refining metals and alloys by treatment with compounds containing fluorin and alkali being set forth and claimed in my companion. application filed May 11, 1921, Serial No. 468,778.

Having thus described I claim is:

1. A casting alloy capable of being machined containing between about 8 per cent; and about 20 per cent. of silicon and atleast about 98 per cent. of the balance being aluminum.

2. A casting alloy capable of being machined containing between 8 per cent. and 15 per cent. of silicon and the balance mostly my invention, what 3. A castui g alloy capable of being machined and consistingmostly of aluminum and silicon, said allo containing substantially one part of silicon to eightparts of aluminum. 7

4;. A casting alloy capable of being machined containing at least 80 per cent. of aluminum, combined with at least 8 per cent. of silicon.

5. A fine' grained, tenacious, machinable alloy made mostly of commercial aluminum and commercial silicon and containing not more than about2 per cent of anymetal having an atomic weight above 60.

6, The process of treating alloys of aluminum and silicon which contains the step of stirring an alkaline fluoridinto the molten mass.

7. The process ofproducing an alloy of aluminum and silicon," wherem the latter constitutes at least about 8 per cent. of the whole which contains the step of stirring into the molten mass at least about-1% per cent. of an alkaline fluorid.

8. The process of producing an alloy of 126 constitutes at least about 8 per cent. of the whole which contains the steps of first melting together commercial aluminum andcommercial silicon, decanting the molten mass to aluminum and silicon wherem the latter remove non-metallic impurities and subsequently incorporatingin .the molten "mass a quantity of a kali fiuorid.'

9; The process of producing an alloy of aluminum and silicon which contains the steps of melting together about 4 parts of commercial aluminum and 1 part of commercial. silicon, pouring the. mixture, 'adding more aluminum in the proportion of from one to three parts of such mixture to each part of aluminum added," and thereafter incorporating with the molten mass at least about 1 per cent of an alkali fluorid.

10. The process of disseminating silicon in aluminum which consists in subjectin the molten ingredents to the action of an a kali fluorin compound.

11. The process of disseminating upward I of 5 per cent. of silicon throughout alugninum to produce a fine grained ductile alloy which consists in subjecting the molten ingredients to the action of one or more other compounds which contain 'fluorm and an alka i.

. 12.511 alloy of aluminum and silicon which contains between 8 per cent. and

per cent. of silicon and whose elongation is signature.

ALADAR. PAOZ. 

